On Tue, Mar 22, 2016 at 12:29 AM, Mattis Lind <mattisl...@gmail.com> wrote:
> >>> Good news - mine worked so fingers crossed for yours too. I now have a > >> functioning PSU again though I've not tried it back in the chassis > yet... > >> > >> Nice! My replacements arrived today and unfortunately I did not have > > such good luck. No smoke or fire, but now I get nothing at all out of > the > > supply. The whine is gone, but there's nothing output at all. The > > fuse/resistor didn't blow (it's still got continuity across it) and the > > transistor I replaced is still fine, but there must be something else in > > the supply that's causing issues... > > > > Blargh. I hate working on power supplies. > > > In this case you have an excellent technical manual and a good schematic > which should help a lot. Working with big SMPSU without schematics or > technical manuals is a not fun. > Yeah, I have actual original copies of the printsets, too. I have no excuse, I just get nervous working on these things. I suppose eventually I'll get used to it. > > So here is my piece of advice directly from my head. > > 1. The PSU has really two AC inputs wired together in the input harness. > You can separate the startup supply part from the SMPSU part. Connect the > startup PSU to a separate AC input and the SMPSU part to a insulation > transformer, a variac and lightbulb in series. 2. Check that the startup PSU, that uses a normal 50/60 Hz transformer > gives the correct voltage. +11 if I remember correctly. > 3. There is a circuit that monitors the input rectified 300VDC voltage and > enables the relay when it has reached a proper voltage. It is a soft start. > Disable it for temporarily. Good idea to check that is working though. If > not the soft start resistors will become overheated when trying to run it > at full load. > The relay (and the circuit driving it) appears to be working -- I hear it click on at power-up (faintly, over the roar of the fans) and click again after power-down. I'll hopefully have some time this week to play around some more, thanks for the suggestions! I'll note that my earlier statement that I was getting "nothing" out of the supply turns out to be slightly inaccurate -- with a load, I get nothing (well, 0.07v) out of the 5V supply; without a load the voltage slowly increases (maybe 0.5V per second). Didn't let it run long enough to see where it ends up ;). Thanks again, Josh > 4. Now you need to have the SMPSU section connected to AC inlet. On one of > the daughter boards there is a switching bias supply. Check that it > generates the +/-12 V and +5V. > 5. Is the main SMPSU switching logic making a nice square wave signal > output. The control board is yet another daughter board. > 6. I disconnected the output terminals from the H-bridge to the transformer > and connected a dummy load to be able to have a look at the output > waveform. > 7. Reconnect the transformer. The main switch produces +5V and +38V. The > 38V is then used on the daughterboards to create all the other voltages, > +/- 12V, +/- 15V, +12V SB, +5VSB (depending on which supply). Is there 38V > here? > 8. There is a crowbar circuit on the +5V output terminals. Check that it is > not tripping. > > > Please note that when working with the +2.5V supply it gets the bias > voltages from the +5V supply. So either get that one working first or > supply bias voltage from a regular PC supply. > > /Mattis > > > > > > > > - Josh > > > > >